A car travels a certain distance at $32\text{km/h}$ and comes back at $68\text{km/h}$. What is the average speed for the total journey?

When a vehicle travels the same distance at two different speeds, say $a\text{km/h}$ and $b\text{km/h}$, the average speed for the entire journey is given by the harmonic mean formula:
$$\text{Average Speed}=\frac{2ab}{a+b}$$
Given $a=32\text{km/h}$ and $b=68\text{km/h}$:
$$\text{Average Speed}=\frac{2\times 32\times 68}{32+68}$$
$$\text{Average Speed}=\frac{4352}{100}=43.52\text{km/h}$$